1. Field of Invention
The present invention relates to a clamping device, and more particularly to a clamping device which is for use on outdoor overhead electrical cables and is configured to optimally compensate the adverse effect brought by thermal expansion of the cables.
2. Description of Related Arts
Referring to FIG. 1 of the drawings, a conventional clamping device, such as a clamping device for overhead high voltage electrical cables 3P, usually comprises a first clamping member 9P having a plurality of first clamping arms 91P, a second clamping member 10P having a plurality of second clamping arms 100P, and a connecting device 4P providing on the first clamping member 9P and the second clamping member 10P.
A free end surface of each of the first clamping arms 91P and the second clamping arms 100P is curved for accommodating the electrical cables 3P when the first clamping member 9P is positioned on top of the second clamping member 10P, while the connecting device 4P is arranged to exert pulling forces against the first clamping member 9P and the second clamping member 10P for clamping the electrical cables 3P therebetween.
There are several disadvantages in association with the above-mentioned clamping device. First, the connecting device 4P is usually arranged to exert very large clamping forces to the two clamping members 9P, 10P because the mounting of the electrical cables 3P must withstand adverse weather conditions. However, when weather condition changes, the electrical cables 3P are subject to thermal expansion. This slight increase in diameters on the part of the electrical cables 3P will cause great stress within each of the electrical cables 3P. When the stress is not properly released or compensated, it may damage the electrical cables 3P or the clamping device. Moreover, when contraction occurs, the diameters of the electrical cables 3P reduce and this may lower the clamping force exerting on the electrical cables 3P. When this happens, the general resistance of the electrical cables 3P may increase and this may increase the temperature of the clamping device. Since the electrical cables 3P are normally supported overhead, it is very arduous for technicians to replace the damaged cables or the damaged clamping devices.
Second, in order to clamp the electrical cables onto the first clamping member 9P and the second clamping member 10P, a technician has to manually operate the connecting device 4P until the first clamping member 9P and the second clamping member 10P securely bias against each other. In this situation, the technician has no way to know when the first clamping member 9P and the second clamping member 10P are secure enough. However, when the electrical cables 3P are tightened too strongly, the electrical cables 3P may be damaged, especially when they are subject to thermal expansion as mentioned above.